Sandisk Ultra II and Windows XP SP2 problem

I purchased the Sandisk Ultra II 2GB. I have a Sandisk USB2 card reader. My Treo 600 sees the card just fine, and can read and write to it. In the card reader, Windows XP SP2 sees the card, but can't read or write to it, and Windows says the card is unformatted even though I put files on it with the Treo.

Windows also says the 2 GB card it is 3.78 GB.

My other card, a Panasonic 512MB, works fine in both devices (including card reader). Windows sees it, can read and write to it. So the card reader works with Windows, just not with the Ultra II card.

Any ideas? Not being able to read and write to the card directly with the PC makes it pretty useless.